Surface plate



Nov. 11, 1958 H. E. RENAUD 2,859,530y

SURFACE PLATE Filed May 12, 1954 ATTO R N EYS United.. States Patenti() SURFACE PLATE Harold E. Renaud, Lansing, Mich., assignor to Ren-Ite Plastics, Inc., Lansing, Mich., a corporation of Michigan Y Application May 12, 1954, Serial No. 429,147 i 6 Claims. (C1. 33-174) The present `invention relates to `granite based sur- .face plates and to a method for producing them. More particularly the invention is directed to resin facedsurfaceplates and to the production of surface plates wherein a resin face is superimposed upon a granite block fby means of an integral surface bond. VIn surfaceplates the surface'accuracy determines the lay-out accuracy of finished sheet metal or sheet plastic forms. The surface becomes the base for coordinating dimensional' tolerances. The accuracy of the surface .plate is,in turn, dependent upon the material constituting its base or support. Metal backing, cellular backing, and truss type support structures are known in the art as support material. The accuracy of the surface reproduced thereon is a constant compromise between thermal coefficients of expansion inthe selected supporting materials and the ability of engineers in call.cula'tinga structure which l'will equally distribute expansionfand contraction effects to minimize disturbance vand distortion of the surface they support.

A surface plate is known in the tool and die art as a plate or surface from which dies, patterns, tools, and .other structures can be layed out accurately. Surface plates-have been made from various materials selected for their `dimensional stability qualities, steel having been used extensively. Granite has also been employed for surface plates of extreme accuracy, but the high cost of finishing a granite surface plate has resulted in a demand forcheaper constructed plates in ,which the .surface accuracy compares favorably with prior surface lplates and in which surface wear is minimized. The .refinishing-.or resurfacing of conventional steel or granite surface plates was expensive and collaterally a surface was sought which would adapt itself to simple renewal. Some advantage exists in the granite surface plate over fthe steel or other metal plates by reason of its relatively low j coefficient of linear and cubic expansion. But .graniteqis subject to the severe criticism of unequal abrasion by reason of the non-homogeneouscharacter of its principal 'ingredients of .feldspar, quartz, and mica. Further, granite is brittle in comparison to steel and shock loading causes chipping and scoring. The physical characteristics of the granite, however, makes it rideal `as a dimensionally stable backing material for a surface plate and the present invention is addressed .to a surface-plate, which in abrasion resistance and dimensional stability surpasses both steel and granite, which f surface plate has an' extended useful life thereby, and vwhen finally rendered unsuitable for extremely accurate `work through prolonged usage can be refaced or resurfaced at Aa minimum of expense.

It is one of the purposes of the present invention to reduce the magnitude of the expansion and contraction problem and to remove the time-.consuming calculations required in designing support structures which will minimize deformation stresses in normal winter and summer thermal ranges.

` "Itis' another object'of this Ainvention toteach a simple nce method for the utilization of shrink free granite based surface plates by the application of a resin face so as to take advantage of thelow thermal coefficients of expansion inherent in granite tmaterial while at the same time minimizing the excessivecost required to reproduce a satisfactorily accurate surface directly upon the granite.

Still another object of this invention is to provide abrasion resistant and dimensionally stable resin .materials capable of forming an integral adhesive bond to granite surfaces while making the granite 'support blocks available for reuse with little or no alteration in their surfaces. l

Other advantages and objects of granite based surfaceplates provided with resin faces will become rreadily apparent to those'skilled in the art of reproducing surfaces and surface plates Vas the description proceeds.

In the drawings:

Figure'. lis a perspective view-l of a rectangular granite block poised over a form built upV around a master surface plate. l'

Figure 2 is a cross-section through Fig. l taken on line II'-II of the master surface plate walled in by forms rising vertically along the sides of the block and showing the parting agent'and the pour of resin.

Figure 3 is aY cross-section view taken Vas in Fig. 2 showing the granite block lowered into position in the form and squeezingresin up between block and form.

l. :Figure'4`is a perspectivev view of a nished smooth curing and removal fromV the forms.`

f GENERAL DESCRIPTION In generali-a granite block 11, selected for its low thermal coeflcients Vof expansion, general rigidity and overall Vresistance to deformation, is Vconformed upon one of its surfaces 1,2 to ar'surfaceY 13 which-is Ysought tobe reproduced thereon., Normally the surface plates 14 are fiat upon the top and Ymay be striated or unstriated depending upon the useto which they Will'be put. For illustrative purposes a plane surface is shown.

A form 15 is prepared to -wall in the master surface plate 14. A coating of parting-agent 16 is applied to the surface 13 .of the master surface plate y14 and is applied also to the walls 15a comprising a portion of the form 15. -A centrally locatedheap -ofrresin material 17 is poured into -the middle of the master surface plate 14 and over the parting agent 16. The surface 12 of the lgarnite block `11 ris llowered Adownwardly upon the heap of Aresin material 17 and the pressure ofthe block 11 forces the equal distribution lof the resiny against -the surfaceto be transferred 13 and a faithful reproduc- SPECIFIC DESCRIPTION A graniteblock 11 is squared and leveled to the size .desired as illustrated vin Fig. 1 'by well known granite working techniques. A form 15 yis prepared to circumscribe or Vencase the edges of amaster surface plate 13 and the walls 15a of the form 15 extend above the `uppermost surface 13 of the master plate 214.4.. The

amount of extension depends largely upon theld'esired thickness of the finished face'o'ffv .the surfacegplate 18.

A coating of parting agent'16 is applied uniformly to 'fing agent by solvent, e. g., butyl acetate.

metal surface plates. 1 surface, by reason of the facing material and by reason ;16..is applied to the inner surface offthe'walls 15a. ofthe fform 1'5. In'g'eneral a wax is used asthe parting-:agent .16, although the application of a coatgofpolished-wax,

then a coat offwhite'lacqueryand finally a'ti'nishing coat of wax provides a more durable A plurality of spacers 19 are positioned upon the mas- 'ter surface plate 14 preferably in '.'a triangular pattern.

The spacers-19' are of equal thickness, for example,'about 1% inch, andthe' thickness ofthe spacers'19 determine A,

.the ultimatethickness of the facing ultimately to become Althe finished surfacelS-of the surfaceplate'. 'The spacers 19 are fashioned preferably from resinous material 17 lhavingrthe samephysicaland chemicalv` characteristics as the resin material 17. :The practice, to prevent displace- 'ment of the spacers-19, is to dip lthe spacers 19 in the resin material 17 priork to positionin'gthern upon the parting agent covered surface 13 of the master plate 14.

t #Resin materiall 17 is poured into a centralheap on the top of the prepared master plate 14. The granite blockl 11, having upon its lower portion the Vdesired Fsurface 12 fori finishing is lowered downwardly within 'the contines of the form walls 15a so las' to force the resin material 17 into intimate engagement with `the block surface 12. The necessary excess resin material 17 flows upwardly between the granite block 11 and the form'walls 15d. The granite block 11 is left resting upon the spacers 19 with the evenly spread resin coat 17 for approximately 24 hours. Removal of the granite blockll is facilitated by the parting agent 16 appliedy to the face 13 of the master plate 14. The form 15 is removed andthe finished resin faced granite based surface plate is complete upon removal of excess part- A smooth 4 system .'wh'en applied v "as the partingagent 16.

-faced surface plate has resulted but a striated, lined,

or grooyed surface plate can be prepared quite as simply -by'altering the master plate 14 if desired. A surface plate in accordance with this specification compares favorably under usage with conventional metal surface ofthe resins comprising'thev face and the rigid, nonfrmetallic and inorganic material comprising the base.

Thebond achieved between resin and granite is of excep- "tional' integrity and the accuracy of the faces of such surface plates can be simply duplicated by these procedures thereby minimizing the cost of normally very Lexpensive surface plates. Surface accuracy measured by steel straight edges and feeler gauges have been checked at .0015 inch with no alteration in procedures.

This accuracyrsurpasses the normal accuracy in steel or The dimensional stability of the o f the shrink free granite back produces a` surface plate f'having greater thermal stability than metals innormal Ytemperature variations and having abrasion resistance 'characteristics on the face surpassing the abrasion resistance in hithertoknown surface plates. p

' The lclearance vselected between the ysize of granite block 11 and the internal dimensions of the form 15 is "such as to permit easy flow of resin material 17 up around the sides of the granite block 11 so that the resin 17 actually flows over the back side of the block 11. Clearances of between about 1A@ and le inch or more vhave 'been satisfactorily employed. In this manner the 4inherent character of the resin used avoidsthe trapping 'of air bubbles which might otherwise pitl the surface `of the finished plate 20 or diminish the strength of the ffinished plate, 20.

' As indicated in` Figs. 1, El and 4, the granite block is rfitted with studs 2.1 for. ease of handling. Y

fr lnorder tomake possiblea resin faced granite backed `platesand is more dimensionally stable both by reason 'ture was obtained. polyfunctional amine hardener of (A) was added and the resulting compositori stirred for ll/z minutes.

surface plate capable of rugged durability in usage, faithful accuracy independent of normal temperature ranges, and possessing excellent integrity of resin bond to granite, it has been necessary to specially formulate a resin material possessing all of these qualities desired upon curing. The following example indicates the preferred composition of the resins making possible resin faced granite based surface plates.

Example 1.-Resin facing composition were admixed in a standard resin kettle until a homogeneous admixture was obtained. Fifty parts byweight of a polyfunctional amine hardener (Bakelite No. 18793), having available active hydrogens to form a reaction product with the epoxy-bis-phenol adjunct, was added to the above admixture and the resulting composition stirred until a uniform resin system was achieved.

Composition B.-l00 parts by weight of the epoxy resin used in (A), 20 parts by weight of lithopone (Permolith), 60 parts by weight of silicon carbide (500 mesh), and one part of blue colorant were admixed and stirred in a standard resin kettle until a smooth admix- Twenty-ve parts by weight of the Immediately prior to suspension of the contoured, granite block -in Ythe mold containing the mastersurface plate, compositions (A) and (B) were admixed and stirred thoroughlyv until complete homogeneity was obtained. Compositon (A) by itself exhibited a somewhat more viscous or thixotropic character than- (B) with the .resulting composite adrnixture being Asuiiciently Huid in nature so that the casting operation was accomplished without entrapment of air bubblesv o r pockets. Upon casting of the granite block in the mold and curing of the resin at room temperature or slightly elevated temperature, a resin faced granite surface plate having unusualrproperties was produced. e

Alternatively, the composite admixture can be prepared directly in a single mixing operation by .utilizing the combined weights of materials from compositions (A) and (B).

While the epoxy resin illustrated -in Example 1 is the preferred basic resin, other resins Vexhibiting similar qualities, such as polyester and polyamide modified polyester and epoxy resins, may be employed. These 'types of resins possess relatively high heat distortion points, good impact resistance and show excellent dimen- .sional stability under prolonged aging conditions. Under 'extreme variances in both thermal and moisture conditions, the dimensional deformation is extremelyV small which, when taken together with the excellent dimensional stability qualities of the granite base,lprovide a very superior surface plate that vhask far greater applicability for extremely accurate lay-out Work than the con ventional metal or metal faced surfaced plates heretofore employed in tooling applications. f

- vBetweenabout three and six parts by weight of epoxy resin, for example, and about one part of hardener (crosslinking agent) is preferably employed, generally permitting achievement of a desired effective epoxy to active hydrogen group ratio of about 1.0 to 1.0. Other-hardeners, such as vthe acid anhydrides, can also be employed but the polyfunctional amines are generally preferred..

Filler materials, such as lithopone, certain diatom'aceous clays, powdered silicates, including lead silicate, and the asian-:seo

like of from preferably 325 to 500 mesh size are useful in giving the proper consistency to the formulation.

Relatively large amounts of very `abrasive material, including the silica carbides generally, more specifically silicon carbide and boron carbide, impart excellent abrasion resistance to the resin surfaceintegrally vbonded to the granite base. Amounts vof from between about 20 and 60 or more percent by weight-of the finishedl resin formulation have been successfully. used. Abrasives having mesh sizesu rom 300 to 600 are Avery satisfactory. Additional absives such as diamond dust andgarnet materials can be used. Carborundum types of silicatecarbon systems, such as carbate and certain precipitated silicas and complex silicates with pronounced silica composition are also operative.

If desired, a hydrophilic bulking material, such as aerogel or one of rthe recently developed bentones, may be employed to control the consistency of the formulation and to keep the abrasive particles from settling in the formulation immediately prior to use or during the curing operation. If rthe ller employed is sufficiently hydrophilic or has suciently small particle size, the bulking material may not be required. 'In any event, the precise amount of the bulking agent will vary with the swelling ability of the hydrophilic material selected, between about one and about tive percent by weight being employed when the abrasive material is boron carbide, for example.

The resin surface of the finished granite based surface plate of the present invention was subjected to comparative abrasion tests with steel and -aluminum plates. A standardized testing procedure was used wherein the percentage of material worn olf in a given period of time was determined, the following data being obtained.

Resin faced granite surface plate 0.008 percent of material worn off in unit time.

Hot roll steel 0.106 percent of material worn oif in unit time. Aluminum 0.278 percent of material worn olf in unit time.

These results indicate that the resin surface was about thirteen times as abrasion resistant as the hot roll steel and about thirty times as resistant as the aluminum sheet under the standard test conditions employed. -It is known that the hot roll steel possesses greater abrasion resistance than granite per se. The very superior abrasion resistance of the resin faced granite based surface plate over the conventional metal or granite surface plate per se can be attributed to the novel resin formulation, as illustrated in Example l, wherein relatively large amounts of highly abrasive materials are included.

OPERATION In operation, resin faced granite backed surface plates co-ordinate accuracy in tool making operations within limits not heretofore available in surface plates of other material where thermal .and moisture variations are encountered. Since the surface accuracy of a surface plate is related directly to its smoothness of surface and its faithful reproduction of planal surface, accuracy checks of surface plates produced by the accompanying methods have shown surface variations not in excess of .0015 inch and planal variations of not in excess of .0030 inch in surface plates having a square size approximately 6 feet by 6 feet. In plates of this size the thickness of granite averaged between three and four inches. The thickness of the resin face has been varied considerably from between about 1/6 of an inch and about l@ inch or more without any material difficulty. Where the granite face is more or less irregular the variations of surface up to Mt of an inch appear to have no appreciable effect upon the observed quality of the finished surface plate 20. It has been found that by elevating the temperatures of the granite two desirable effects are obtained. Cross-section studies indicate the complete yelimination of air `bubbles anda more rapid cure of the resin 'is brought about. Variations brought about by thermal variations after .curing are noted elsewhere in this specification.

When it becomes necessary to retinish a surface plate prepared in accord with this invention thesurface plate 20 need vonly be solvent cleaned and recast with anew resin face 18 which will integrally bond to lthe original or previously replaced surface. The simplicity of preparation of resin faced granite based lsurface pla'tes'hasl placed them in great dem-and 'in every industry requiring an extremely high order lof tool -co-ordination. The economy of productionof such surface plates by reason of the Vprocedural simplicity in their preparation Qhas resulted in great tooling cost reductions. The faithfulness of reproduction and the unusual durabilityof such resin faced granite based surface plates has assured their demand. The restoration available for worn surfaces has avoided obsolescence on wear.

This application is a continuation-in-part of U. S. application Serial 331,255 filed 1953 January 14 wherein disclosure is made of the use of abrasive materials and of U. S. application Serial 404,013 led 1954 January 14.

5Having described a specific embodiment of the invention, I claim:

1. In a surface plate, a base comprising a natural stone characterized by a low coeflicient of thermal expansion and high dimensional stability, said base having an upper surface in general conformity with a reference surface to be reproduced, said base having bonded to said surface a coating of an epoxy resin composition comprising an epoxy resin andan active hardener agent in the ratio of about 1.0 of the resin-1.0 of the hardener agent, said coating presenting a smooth, hard and abrasion resistant top face which is an accurate reproduction of said reference surface, said epoxy resin comprising a condensation product of a chlorohydrin and a polyphenol under alkaline conditions.

2. A surface plate in accordance with claim l, in which said chlorohydrin is epichlorohydrin and said polyphenol is bis-phenol-A.

3. A surface plate comprising a base of rigid, nonmetallic and inorganic material characterized by a low coefficient of thermal expansion and high dimensional stability, said base having an upper surface in general conformity with a reference surface to be reproduced, said base having bonded to said surface a coating of an epoxy resin composition comprising an epoxy resin and a hardener having an active hardener agent in the ratio of about 1.() effective resin-1.0 effective hardener agent, said coating presenting a smooth, hard and abrasion resistant top face which is an accurate reproduction of said reference surface, said epoxy resin comprising a condensation product of a chlorohydrin and a polyphenol under alkaline conditions.

4. A surface plate comprising a base `of natural stone characterized by a low coefficient of thermal expansion and high dimensional stability, said base having an upper surface in general conformity with a reference surface to be reproduced, said base having bonded to said surface a coating of an epoxy resin composition comprising an epoxy resin and a hardener having an active hardener agent in the ratio of about 1.0 effective resin-1.0 effective hardener agent, said coating presenting a smooth, hard and abrasion resistant top face which is an accurate reproduction of said reference surface, said epoxy resin comprising a condensation product of a chlorohydrin and a polyphenol under alkaline conditions.

5. A surface plate comprising a base of granite having an upper surface in general conformity with a reference surface to be reproduced, said base having bonded to said surface a coating `of an epoxy resin composition comprising `an epoxy resin and a hardener having an active hardener agent in the ratio of about 1.0 effective resin-1.0 elfective hardener agent, said coating presenting a smooth,

hard and abrasion resistant'top face which is an accurate reproduction of said reference'surface, said epoxy resin comprising a condensationproduct of a chlorohydrin and a polyphenol under alkalineA conditions.

6. A surface plate comprising a base of natural stone characterized by a low coefficient of `thermal expansion and high dimensional stability, said base having an upper surface in general conformity with a reference surface to be reproduced, said base having bonded to said surface a coating Aof an epoxy resin composition comprising an epoxy resin comprised of a'produce of condensation under alkaline conditions of epichlorohydrin and bis-phenol-A, and a hardcner having an active hardener agent in the ratio of about 1.0 effective resin-1.0 eiective hardener agent,

said coating presenting a smooth, hard and abrasion re-vsistant top face which is an accurate reproduction of said reference surface.

UNITED STATES PATENTS Myers Apr. 3, 1923 Barringer July 16, 1929 Brault Apr. 28, 1936 Marshall Mar. 12, 1940 Sayre June 24, 1941 Saunders Dec. 14, 1943 lMilligan Apr. 3, 1951 Ferrell Feb. 2, 1954 Raskin June 26, 1956 FOREIGN PATENTS Great Britain Feb. 18, 1943 OTHER REFERENCES Concrete, pages 12 and 45, June 1949. 

